Just get a Weber Smokey Mountain (bullet). It'll easily run many hours on a load of charcoal and hold a steady temperature. Comes in three sizes, 14", 18" and 22".
I think the 14" is too small but that would be dictated by what you can fit aboard.
Note that the WSM is a smoker, not a grill, and is completely unsuitable for burgers, steaks etc. The Weber Jumbo Joe is a great portable grill, and I actually managed to smoke a small turkey on a Jumbo Joe once.
Go here http://tvwbb.com for more.